(1) Field of the Invention
The present invention relates to a structural element and more particularly to a load-bearing structural element useful, for instance, as wall element, for structures, supports, bridges, vehicles, and others.
(2) Description of the Prior Art
Structural elements which consist of two or more structural shells or panels of at least one sealing packing lying between the edges of the shells or panels, and a cavity hermetically enclosed by them have been described heretofore. In the cavity of said elements pressing means, for instance, honeycomb plates with interposed solid plates, for instance, metal plates and associated sealing plates, for instance, foam-plastic plates which can be covered with vapor-proof sheets, for instance, aluminum foils, are provided and at least one of the structural shells or panels is arranged so that it can shift its position flexibly, or can be bent, for instance, concavely against the seal, and a vacuum is produced within the cavity.
As a result of the elimination of air counterpressure or back pressure within the structural element, the external air pressure causes at least bending or sagging of the flexible structural shells or panels and/or in particular a change in place of the structural shells in direction towards each other by compression of the seal and the cavity inserts. As a result of said atmospheric pressure, the inserts in the cavity, particularly the honeycomb webs or straps, are placed under tension and press with this force against the interposed metal plates and the inner sides of the structural shells. This results in increased resistance to bending of the inner plates and intermediate panels or sheets supported in this manner, as well as of the outer structural shells or panels, in the event that they are acted on by load in the direction of their planes. In the case of a vacuum, this amounts, perpendicular to the outer shells or panels and the honeycomb plates on the surfaces of the metal plates arranged in the cavity and other intermediate plates, to about 10 tons per sq.m.
This atmospheric pressure is of randomly caused order of magnitude. It is determined by the gravitational force of the earth on the atmosphere, the composition of the air as a mixed gas, and the height of the atmosphere.